At Oak Ridge National Laboratory (ORNL), Tennessee, scientists are applying 3D printing to recycle and reuse a common byproduct of the manufacturing industry.
Produced in large quantities as waste from the paper making process and biomass energy conversion, lignin is finding new purpose as a reinforcement for composite FFF filament.
“ORNL’s world-class capabilities in materials characterization and synthesis are essential to the challenge of transforming byproducts like lignin into coproducts, generating potential new revenue streams for industry and creating novel renewable composites for advanced manufacturing,” explains Moe Khaleel, associate laboratory director for Energy and Environmental Sciences at ORNL.
ORNL project lead Amit Naskar adds:
“Finding new uses for lignin can improve the economics of the entire biorefining process.”
Barking up the right tree
Lignin is the essential structural tissue of tree bark and wood. With high carbon content (e.g. 63.4% in aspen trees) it is incredibly rigid. To enhance this valuable property, in ORNL’s new recipe lignin is combined with conventional plastic, a low-melting nylon, and carbon fibers.
The end product, a desktop-3D printable filament, exhibits good adhesion and excellent mechanical properties. According to ORNL collaborator Ngoc Nguyen, “[The] structural characteristics of lignin are critical to enhance 3D printability of the materials.”
An advance on a previous lignin study published by the ORNL team in July 2018, in this most recent mixture, lignin constitutes between 40 and 50% of the overall material, a high concentration that has never been achieved before.
Lignin is currently on the market in some areas as a PLA-based material called BioFila by the company twoBEars, however the company has had little-to-no activity in recent years.
ORNL’s lignin composite filament is patent-pending, and subject to further development over the course of the lab’s byproduct discovery.
A full paper discussing the latest lignin developments from ORNL titled “A path for lignin valorization via additive manufacturing of high-performance sustainable composites with enhanced 3D printability” is available to read online in Science Advances journal. The article is co-authored by Ngoc A. Nguyen, Sietske H. Barnes, Christopher C. Bowland, Kelly M. Meek, Kenneth C. Littrell, Jong K. Keum and Amit K. Naskar.
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Featured image shows one possible molecular structure of lignin. Image by KIT-IKFT, Marcus Breunig